Ivory, opalescent glasses



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IVORY, OPALESCENT GLASSES No Drawing. Application June 27, 1957 SerialNo. 668,290

7 Claims. (Cl. 106-52) The present invention relates to opaque glassesand it has particular relation to novel compositions yielding opaqueglasses having a pleasing ivory color. This application is acontinuation-in-part of our copending application Serial No. 583,912,filed May 10, 1956, now abandoned.

Opaque glasses have found widespread adoption as a structural medium,particularly in the construction of storefronts, kitchens, bathrooms andthe like. Production of these glasses in a range of colors has been verywell standardized and even today, when material shortages havenecessitated variations in batch compositions, most of the colors can beobtained by either the pot casting method or in continuous furnaces.These glasses are annealed according to conventional practices and arepolished on at least one surface in accordance 'with'conventional,polished plate glass practices. The following US. patents describe someof these glasses: 1,956,176 (cream), 2,224,469 (opal base), 2,237,042(red or pink), 2,282,601 (ivory), 2,394,502 (white), 2,599,349 (green),2,683,666 (ivory) and 2,776,900 (tan).

Difficulty has been experienced, however, in compounding an opaque glasshaving an ivory color which is satisfactory to the trade. It is wellknown that an ivory, opaque glass can be made with fluorine, uranium andselenium as the colorants. The importance of the use of uranium in otherfields has restricted its use for glass making to the extent that it isnot available.

It is an object of the present invention to provide an ivory, opaqueglass having definite radiant energy reflectance values and which may bemanufactured by conventional pot casting or continuous plate glassmanufacturing procedures.

Another object of this invention is the provision of an ivory, opaqueglass which does not require the 'use of uranium as a colorant. chromiumoxide in a glass produces a green color and that selenium produces apink color. We have discovered that a pleasing ivory colored, opaqueglass is produced when the proper proportions of chromium oxide andselenium are employed in glasses composed of 60 to 75 percent S110 to 18percent Na O, O to percent K 0, 0 to 10 percent CaO, 0 to 12 percentZnO, 0 to 12 percent B210, 2 to 12 percent A1 0 0 to 2 percent AS205, 1to 7 percent F and 0 to 5 percent TiO In accordance with the presentinvention, readily reproducible ivory, opaque glasses, are provided.These glasses contain as the essential coloring ingredients 1 to 7percent by weight fluorine, 0.005 to 0.1 percent by weight chromiumoxide, and 0.01 to 0.2 percent by weight selenium. Calculatedcompositions of some glasses which are within the purview of the presentinvention are set forth in the table below. These glasses can be madefrom conventional glass forming compounds.

The oxygen equivalent of fluorine is set forth in the table because ofthe manner of calculating the composi tion of the glass. The fluorineshown in the composition in the tables is understood to be present inthe glasses It is well known to the art that cost of the batch. It ispreferred that the total weight Patented Aug. 4, 1959 Table Ingredients1 2 3 4 5 6 7 08.2 69.6 69. 14.4 14.9 14. 1.9 0.7 2. 0.7 6.0 0. 1.7 3.4.6 .6 8.8 3.2 9.0 9 .9 0.8 1.0 0.9 .7 .7 3.0 5 0 2. 9 1.4 .0 0. 0.02 0.0.01 0.02 0.02 e 0.06 0.12 0.06 0.03 0.03 0.04 0.06 Oxygen equivalentoffluorine 1.2 1.3 1.2 -1.3 -1.3 2.1 1.3

1n some combined form but not as a gas. 'It is not known exactly howthis fluorine is combined, but it is probably combined as a fluoridesuch as NaF, KF or CaF In an analysis of a glass, it is customary toanalyze only for the elements and then list the presence of theseelements in the glass as oxides. fluorine is present in a glass, it isprobably present as a fluoride compound with a cation in the glass andthus replaces a stoichiometric equivalent of oxygen 'with this cation.Thus, it is convenient to show the amount of fluorine in percent byweight as fluorine and then subtract from the sum total percentages ofthe glass composition based on oxides, its stoichiometric equivalent ofoxide in percent by weight.

Silica is the principal glass former. A range of SiO between 60 to 75percent by weight is preferred. The durability of a glass containingless than 60 percent by weight SiO is poor and it is difficult to melt aglass containing over 75 percent by weight SiO There is also a tendencyfor glass containing'more than the desired maximum of SiO to devitrify.

The alkali metal'oxides, Na O and K 0, are the principal fluxes. Li Omay be used to replace part of the Na o and K 0, however, this materialincreases the of alkali metal oxides in the glasses of the presentinvention be within 13 to 21 percent by weight of the glasses.

alkali metal oxides are difiicult to melt. The glasses .have poordurability when the total alkali metal oxides metal oxides and fluorineis required to compensate for in the glasses. crystals.

the stiffness imparted to the glasses by the alumina. The glasses havetoo narrow a working range if less than 2 percent by weight of A1 0 isemployed.

Up to 10 percent by weight of CaO may be included CaO tends to producesmaller fluoride For glasses wherein an opacity with smaller fluoridecrystals is desired, a high percentage of fluorine is required. Glassescontaining above 10 percent by weight (1210 require an extremely highpercentage of Where the maximum opacity with the minimum amount offluorine is desired, the glasses should be substantially free from CaOOther bivalent metal oxides such as ZnO and Ba() may be employed. Whensuch bivalent metal oxides are used, the maximum total Weight of thebivalent metal ployed as a refining agent. Other refining agents may Incases where some Glasses having below 13 percent by weight be usedsingly or in combination providing that they do not affect thereflectance and color properties of the glasses.

Fluorine is used as an opacifying agent. It also acts as a flux and acolorant. The amount of white or opacity has a very great effect on theintensity of the ivory color. It is preferred to have between 2.5 and3.0 percent by weight F in the glasses, although as high as 7 percent oras low as 1 percent by weight may be used, depending upon thepercentages of the other constituents, the degree of annealing and theintensity of the color required. If too much fluorine is included, theglasses will opacify too rapidly, thereby forming dense, opaque glasseshaving a lighter color than that desired. If too little fluorine isemployed in combination with the other colorants, colored glasses havinga milky or translucent appearance are produced instead of glasses havingthe desired opacity.

Selenium and chromium oxides are the colorants employed in combinationwith fluorine to produce the ivory, opaque glasses. Only small amountsof these colorants are required. The amount of selenium may vary from0.01 to 0.2 percent by weight and the amount of chromium oxide may varyfrom 0.005 to 0.1 percent by weight. The balance between the fluorineand the coloring agents is necessitated by the manner in which theglasses are formed.

The glasses of the invention may be produced from conventional glassmaking materials properly compounded and thoroughly mixed so as toyield, when reacted, glasses of the desired ultimate composition.Suitable batch materials include sand, soda ash, potassium carbonate,sodium nitrate, arsenious oxide, nepheline syenite, feldspar, sodiumsilico fluoride, fluorspar, zinc oxide, barium carbonate, titaniumdioxide, chromium oxide and selenium metal.

Various size pots or crucibles may be employed and the meltingtemperatures and times will vary according to the amount being formed.The temperatures and melting conditions herein recited may be employedto make 8 pounds of glass in a refractory pot in a furnace heated by thecontrolled combustion of natural gas.

An empty pot is preheated in the furnace at a furnace temperature ofabout 2200 F. A portion of the mixed batch is ladled into the preheatedpot and the furnace temperature is gradually increased until it reachesapproximately 2500 F. in one hour at which time a second charge of theremaining batch is added to the pot. The pot and its contents are heatedfor an additional hour and a half and the furnace temperature isgradually increased to 2650 F. At the end of this time, the glass isformed in a molten condition. The molten glass is then held at a furnacetemperature of 2650 F. for one and one-half hours to permit theconclusion of the chemical reactions, the exclusion of gases and thesubstantial homogenization of the glass. It is desired that the glass beproduced under neutral to slightly oxidizing conditions in the meltingfurnace or container.

The refined glass is cooled to approximately 2200 F. and the pot isremoved from the funnace. The contents of the pot are poured on a castiron table where the glass is rolled in the form of a plate. The plateis placed in a kiln and cooled from a temperature of about 1050 F. toabout 850 F. at a rate of about 4 F. per minute. During this coolingoperation, the glass is annealed, the fluoride crystals are formed andthe color develops as a result of using a combination of the properproportions of fluorine and the other colorants. After cooling, theglass may be ground and polished.

The glasses set forth above have colors which may be described as havingcertain radiant energy reflectance values over the visible portion ofthe spectrum. The glasses of the present invention have radiant energyreflectance values of from 23 to 43 percent at 400 millimicrons, 26 to46 percent at 450 millimicrons, 31 to 51 percent at 500 millimicrons, 40to 60 percent at 550 millimicrons, 45 to 65 percent at'600 and 650millimicrons, and 48 to 68 percent at 700 millimicrons.

The reflectance values of the glass set forth in column 1 of the tableabove are set forth below to illustrate a glass having reflectanceproperties within the specified 'Although the present invention has beendescribed with respect to specific details of certain embodimentsthereof, it is not intended that such details be limitations upon thescope of the invention except insofar as set forth in the followingclaims:

We claim:

1. An ivory, opaque glass consisting essentially of the followingingredients in percent by weight: 60 to 75 percent SiO 13 to 21 percentalkali metal oxides selected from the group consisting of 5 to 18percent Na oand 0 to 10 percent K 0, 2 to 12 percent A1 0 0 to 10percent CaO, 0 to 12 percent ZnO, and 0 to 12 percent BaO, the sum ofthe bivalent metal oxides being not greater than 12 percent whenpresent, 0 to 2 percent AS205, 0 to 5 percent TiO 1 to 7 percent F,0.005 to 0.1 percent chromium oxide and 0.01 to 0.2 percent selenium.

2. An ivory, opaque glass as defined in claim 1, said glass havingradiant energy reflectance values relative to pure magnesium oxide offrom 23 to 43 percent at 400 millimicrons, 26 to 46 percent at 450millimicrons, 31 to 51 percent at 500 millimicrons, 40 to 60 percent at550 millimicrons, 45 to 65 percent at 600 millimicrons and at 650millimicrons, and 48 to 68 percent at 700 millimicrons.

3. A glass having substantially the following composition wherein theingredients are set forth in percent by weight: 70.4 percent SiO 14.9percent Na O, 2.0 percent K O, 0.6 percent CaO, 9.6 percent A1 0 0.9percent AS205, 2.7 percent F, 0.02 percent Cr O and 0.06 percent'Se, thetotal exceeding percent by an amount of oxygen stoichiometricallyequivalent to the amount of fluorine present.

4. A glass having substantially the following composition wherein theingredients are set forth in percent by weight: 70.1 percent SiO 15.0percent Na O, 2.0 percent K O, 0.6 percent CaO, 9.5 percent A1 0 0.9percent As O 3.0 percent F, 0.05 percent Cr O and 0.12 percent Se, thetotal exceeding 100 percent by an amount of oxygen stoichiometricallyequivalent to the amount of fluorine present.

5. A glass having substantially the following composition wherein theingredients are set forth in percent by weight: 71.0 percent SiO 14.9percent Na O, 2.0 per cent K 0, 9.6 percent A1 0 0.9 percent A5 0 2.7per- 5, cent F, 0.02 percent Cr O and 0.06 percent Se, the totalexceeding 100 percent by an amount of oxygen stoiohiometricallyequivalent to the amount of fluorine present.

6. A glass having substantially the following composition wherein theingredients are set forth in percent by Weight: 68.2 percent SiO 14.4percent Na O, 1.9 percent K 0, 0.7 percent 0210, 3.4 percent ZnO, 8.8percent A1 0.8 percent AS205, 3.0 percent F, 0.01 percent Cr O and 0.03percent Se, the total exceeding 100 percent by an amount of oxygenstoichiometrically equivalent to the amount of fluorine present.

7. A glass having substantially the following composition wherein theingredients are set forth in percent by weight: 68.2 percent SiO 14.4percent Na 0, 1.9 percent K O, 0.7 percent CaO, 3.4 percent BaO, 8.8percent A1 0 0.8 percent As O 3.0 percent F, 0.01 percent Cr O and 0.03percent Se, the total exceeding per-'- cent by an amount of oxygenstoichiometrically equivalent to the amount of fluon'ne present.

References Cited in the file of this patent UNITED STATES PATENTS2,360,280 Rolph et al Oct. 10, 1944 2,416,392 Hood Feb. 25, 19472,683,666 Duncan et a1. July 13, 1954 OTHER REFERENCES Tooley: Handbookof Glass Manufacture, 1953, Ogden"

1. AN IVORY, OPAQUE GLASS CONSISTING ESSENTIALLY OF THE FOLLOWINGINGREDIENTS IN PERCENT BY WEIGHT: 60 TO 75 PERCENT SIO2 13 TO 21 PERCENTALKALI METAL OXIDES SELECTED FROM THE GROUP CONSISTING OF 5 TO 18PERCENT NA2O AND 0 TO 10 PERCENT K2O, 2 TO 12 PERCENT AL2O3, 0 TO 10PERCENT CAO, 0 TO 12 PERCENT ZNO, AND 0 TO 12 PERCENT BAO, THE SUM OFTHE BIVALENT METAL OXIDES BEING NOT GREATER THAN 12 PERCENT WHENPRESENT, 0 TO 2 PERCENT AS2O5, 0 TO 5 PERCENT TIO2, 1 TO 7 PERCENT, O TO2 PERCENT 0.1 PERCENT CHROMIUM OXIDE AND 0.01 TO 09I PERCENT SELENIUM.